Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/f9b4bd2a4713
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #15431 from svic/Bug_960222

Bug 960222: Fix debug message and typo in NFC Manager.

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https://hg.mozilla.org/integration/gaia-central/rev/9f7de65e7495
Author: Garner Lee <garner.lee@telekom.com>
Desc: Bug 960222: Fix debug message and typo in NFC Manager.

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "6a1273aa99423bed1c7fa2f774491a8ff1d9e955", 
+    "revision": "f9b4bd2a4713efa6ffaebdc819ff06e44dfa2779", 
     "repo_path": "/integration/gaia-central"
 }